The invention relates to a fastening means comprising a threaded bolt and a fastening element adapted to be fastened on the threaded bolt.
It is known to use fastening bolts, on which parts can then be mounted, in the automobile car body industry, the ship-building industry, and other applications. In the case of automobiles, for example, those parts are cables, lines, and the like. The fastening bolts are mostly welded thereon and will stand out from the carrier. They normally are threaded. However, it is also known to groove them.
Fastening elements of plastic material are known which can be engagingly pushed over the fastening bolts. The fastening elements are mostly sleeve-like and have inner protrusions which are resilient and engagingly cooperate with the thread of the fastening bolts. It is in this way that the fastening element may be mounted on the bolt by simply pushing it over the bolt or delivering a blow onto it. Removal is possible later, but requires the fastening element to be turned off like a nut.
The known fastening means are efficient, but they sometimes have the disadvantage that the fastening element is allowed to rotate on the fastening bolt or rotary forces are not counteracted by a major obstacle.
Therefore, it is the object of the invention to provide a fastening means or fastening element which can be mounted in a particularly firm fashion on a fastening bolt, but can also be removed again and can be used a plurality of times. The inventive fastening element of plastic material comprises two portions which, however, are formed as a unit, particularly in a plastic injection molding process. The first portion is a hollow part having a throughgoing axial passage the cross-section of which is polygonal. The wall of the passage has resilient portions such that they are radially outwardly deformed if the first portion is pushed onto the threaded bolt under a more or less large axial force. The axial force to be exerted here should not be so large that the second element portion which can be sheared off or broken off is released from the first one. Therefore, the prefabricated fastening element may be pre-assembled by pushing it onto the threaded bolt.
The annular second portion which is formed to one end of the first portion has an inner cross-section which is dimensioned such that it can be pushed over the outer side of the first portion under radial inward deformation of the resilient wall portions in an engagement with the thread. In dependence on the hardness of the material used for the fastening element, the thread tips engage the resilient wall portions more or less deeply so that this manner prevents the fastening element from being stripped off the threaded bolt. It is impossible for the resilient wall portions to slip away sidewards because the second element portion prevents them from doing so. If the fastening element is to be removed from the threaded bolt it requires to be unscrewed from the thread of the fastening bolt.
To facilitate an introduction of the threaded bolt into the first portion, the passage of the first element portion, according to an aspect of the invention, is provided with a conical entrance portion at the end opposite to the second element portion.
The first element portion is preferably shaped like a cage and, for example, has a plurality of circumferentially spaced ribs or webs extending in an axially parallel manner which undergo radial deformation while striking on the thread of the fastening bolt. Therefore, the diameter of the circle which the insides of the ribs or webs describe is somewhat smaller than the tip diameter of the thread of the threaded bolt. To make it easier to radially deform the ribs, webs or other resilient wall portions, one aspect of the invention provides for axially parallel slots to be located between these portions.
The second annular element portion has an inner contour which approximately matches with the outer contour of the first element portion with the contour being preferably non-circular. In this way, a torque which readily is transmitted to the inner element portion can be applied to the outer or second element portion in order to rotate the fastening element. Disassembly is performed by unscrewing it as was mentioned previously. To this effect, the bolt thread cuts its way into the segments or wall portion of the inwardly biased cage. If a cutting element is contemplated at the upper end of the threaded bolt the thread may also be formed in by chip removal. It is possible to screw it on and off for a repeated assembly and disassembly.
According to another aspect of the invention, a provision is made for the first and second element portions to have locking portions which get into engagement with each other when the second element portion is completely pushed over the first element portion. This interlocking may be made largely unreleasable and, according to another aspect of the invention, may be configured in such a way, for example, that the first element portion, at the end opposed to the second element portion, is formed with a flange to which locking portions are formed, in turn, which extend towards the second element portion with a space to the outer side of the first element portion, and cooperate with a locking recess of the second element portion.